1. Field of the Invention
This invention relates to a method and an apparatus for embedding cable or cable-like members under water at desired depths in either a soil layer, generally referred to as sand overburden or in a substantially solid rock layer. It particularly relates to a method and apparatus for cutting down into rock or hardened surface beds to form a trench; for fluidizing the soil and loosened rock in front of the apparatus; and for conveying this fluidized earthen materials to the back of the apparatus to set the materials back into the trench for easy travel of the apparatus along and for embedding the cable in the seabed or waterbed.
2. Description of the Prior Art
When embedding or burying electric cable or cable-like members, such as plastic pipes at varying depths beneath the bed of rivers, lakes, or other bodies of water, it has been known to employ a cable carrying apparatus which is pulled along the waterbed by a winching device which is either ashore or afloat.
Such a cable embedding apparatus is disclosed in U.S. Pat. No. 3,638,439. The apparatus comprises a waterbed soil depressor member carrying the cable and extending down into the soil along a path cut out by a plurality of jets connected to a source of fluid under pressure for creating a jet flow at a high flow rate and a low pressure to temporarily liquify the waterbed soil in the path of the cable. One of the major drawbacks to this apparatus is that it is not easily adapted to cut through solid surfaces or rock layers. Another drawback is that the depth to which the cable is embedded is restricted to the length of the depressor or cable carrying unit extending into the soil in that the depressor is fixedly secured to the apparatus.
More recent designs provided for both the fluidizing or liquifying of the waterbed soil or sand overburden and the cutting through of rock strata. Such an apparatus is disclosed in a patent application filed on Aug. 29, 1986 bearing U.S. Ser. No. 06/902,146 in the application of Harry Johnson, et al. having the same assignee as the subject patent application. This apparatus employs a soil embedder depressor assembly comprising a bellmouth and a low pressure jet assembly for fluidizing the soil or sand overburden. For deeper embedment of the cable, this apparatus employs a rock embedder depressor assembly comprising a rotary blade attached to and extending from the rear of the soil embedder depressor assembly. Pivotal movement of both the soil embedder depressor assembly and the rock embedder depressor assembly of this patent application relative to pontoons allows for a deeper reach down into the waterbed with the rock embedder depressor assembly adapted to extend deep into the rock layer.
This latter design for a cable embedding device, however, is complicated in that it employs one means for burying the cable in the sand overburden and a separate means for burying it in the rock layer.
The previously known art provides a means for fluidizing the soil or rock in front of the cable embedder with the fluidized material remaining directly in the path of the embedder whereby a substantial amount of frictional forces still exist resulting in a substantial pulling or towing force for dragging the embedder along the waterbed or the dugout trench.
Other cable embedding devices are described in U.S. Pat. Nos. 3,333,432; 3,338,060; and 3,504,504. U.S. Pat. No. 3,504,504 provides a jaw-scoop type of trenching apparatus with a plurality of eductor jet means and eductor tube means for removing the earthen materials from the cut trench. However, such earthen materials are ejected into the water above the cable embedder, which most likely results in permanent soil displacement.
There is, therefore, lacking in the prior art a teaching of a cable embedder assembly which is simple and compact in design, and is adapted to perform both as a soil cable embedder and a rock cable embedder. There is further lacking in the prior art such an apparatus which conveys the soil and/or rock slurry from in front of its path of travel to the back of the apparatus for backfill of the earthen materials as the apparatus travels along the waterbed or in the trench in the trench making operation.
There is also lacking in the prior art a combination rock-soil cable embedder which easily travels along the waterbed and is adapted to cut down into the rock in a gradual slope for the forming of a trench. There is further lacking in the art, a combination rock-soil cable embedder assembly comprising a rotary saw which is supported by a framework which includes means for lowering the rotary saw and the cable guide member together as a unit and allowing such positioning in at least a two degree freedom of movement with respect to the vertical extent of the embedder assembly. In addition, there is lacking in this type of device a cable guide member with a depressor which is a substantially curved unitary member employed for both a rock and a soil cable embedding operation. This type of apparatus further lacks means for applying both a pressurized jet flow and negative pressure along the front of the apparatus for fluidizing the earthen materials, picking them up and conveying them along the length of the apparatus and then discharging them back into the trench directly behind the cable embedding apparatus.